As known, cylinder blocks cast of aluminum or aluminum alloy have the primary benefit that they are light in weight in comparison with ferrous materials, so offering the opportunity of achieving high power/weight ratios in the internal combustion engine. At the same time such cylinder block are not as strong as similar cylinder block of ferrous materials and are not as well able to withstand the stresses encountered in engine operation.
While the cylinder block made of lightweight metals are useful for internal combustion engine having a low-medium power, wherein the pressure of the gases produced by combustion into the cylinder of the cylinder block usually does not exceed the threshold value of 180-200 bar, they are particularly stressed for high power internal combustion engine, wherein the pressure of the gases produced by combustion exceeds 200 bar.
In particular, two parts of the internal combustion engine which are subject to particularly high stresses are: the connection between the cylinder block and a cylinder head, which cooperates with a piston to define a combustion chamber, and the connection between a lower part of the cylinder block which supports the bearings of a crankshaft and associated caps supporting the lower part of the bearings which are bolted onto the cylinder block at the lower part thereof.
In order to improve the stiffness of the cylinder block, cylinder blocks including lightweight metals and including a reinforcing insert, such as an insert-molded ferrous skeleton, made of a heavier and stiffer metals such as cast iron are known.
The reinforcing skeleton, nevertheless, creates a barrier for the connection between a lubrication gallery, generally defined in the lightweight metal constituting the cylinder block, and the bearings to be lubricated, which result in a complicated and difficult to manufacture layout of the bearings lubrication circuit.